From the author of

From the author of

As languages go, I love C++. As development environments and productivity
tools go, I have had a great deal of productive good fun working with
Borland's Delphi. I am the opposite of a language bigot; I like all great
languages and tools. As great languages and tools go, there is no greater
support for debugging and testing code then Microsoft's .NET Framework. The
System.Diagnostics namespace in .NET has more classes and code for helping you
debug and test your applications than any other tool by a mile.

One of the benefits of being the latest and greatest tool is that you have
the opportunity to leapfrog over the competition (at least for a short time).
Microsoft has clearly done that. The "Softies" have taken techniques
that you and I have been using for years, extending them, and incorporating them
into .NET. Because the debugging tools in .NET could easily take up the pages of
an entire book, we'll have to limit our discussion to an appetizer. What I
want to talk about in this article is the BooleanSwitch.

A BooleanSwitch is the notion of externalizing a value that can be
read and used to decide whether some chunk of code should run. This is not a new
concept; you can easily implement it with an .INI file (or any kind of file).
What is new is that Microsoft has recognized it as a valid debugging-and-testing
strategy and has made it part of .NET using XML as the storage medium. The
benefit is that this old standby is now and forever part of a common toolset. We
can move on to other things.

This really is what the role of mainstream companies is: Identify what works
and make it ubiquitous. (Gutenberg and the Bible/printing, Ford and the
automobile, Gates and the BooleanSwitch, and on it goesstretching forward
and backward in time.) Making something part of the common vernacular permits us
to proceed to the next thing. This is progress.

Defining the XML Switch

XML is a self-describing, text-based language. It is ideal for simple tasks
such as storing configuration information and complex tasks such as transporting
the description and data that describes an object as text across the Internet.
Instead of each programmer figuring out how to store external configuration
information, we can all settle on the public standard, XML.

.NET supports an application configuration file for executables. Such a file
has the same name as your executable assembly with a .config extension. Placed
in the same directory as an executable named HasBooleanSwitch.exe, the
application configuration file would be named HasBooleanSwitch.exe.config.

TIP

There is a machine.config file that serves a similar purpose as the
application configuration file, but on a larger scale. Technically, you could
put switch information in the machine.config file, located in
<installdrive:>\\winnt\Microsoft.NET\Framework\<version>\\CONFIG,
where <installdrive> is the drive that Windows was installed on and
<version> is the version number of the .NET framework you are
configuring. However, it is a better practice and not especially difficult to
define a configuration file for each application.

The configuration file needs to contain well-formed XML, and the
BooleanSwitch class will be looking for a specific tag as well as specific
attributes for that tag. Listing 1 contains contents of a configuration file
that has information relevant to only our switch in it.

Don't use line numbers in your XML document. Line numbers were added for
reference. The first statementline 1is required for an XML document.
The version attribute indicates the version of XML and the second attribute,
encoding, is optional. The encoding attribute indicates how the text is encoded.
UTF-8 is a Unicode encoding.

Line 2 starts a <configuration> block ended by the
</configuration> tag. Tags in configuration files are case-sensitive. The
<configuration> tag indicates that information in this section is
application configuration information.

The <system.diagnostics> tagopened on line 3 and closed on line
7contains information that is relevant to .NET classes in the
System.Diagnostics namespace. We will define our BooleanSwitches in this
sectionbetween the opening and closing <system.diagnostics>
tags.

The <switches> tag contains our BooleanSwitches. In our example, we
have added a switch named MySwitch with a value of 1. For BooleanSwitches, the
value is treated very simply as a Boolean value. Any non-zero value is treated
as True, and 0 is treated as False. Listing 1 defines a switch named MySwitch
that is enabled.

TIP

Other configuration tags include the <remove> and <clear> tags,
which can be used to remove individual switches or to clear all switches.

Ending tags can be abbreviated to /> as in <clear />, which becomes
the complete element for the clear tag.

The benefit of using XML is that the syntax for defining the switch becomes a
standard that can be codified. This standard is codified in the
System.Diagnostic.BooleanSwitch class.